DE10058174A1 - Ultrasonic probe especially for manual testing, has one or two digital cameras integral with it and directed at the test piece surface for precise locating of probe measurements - Google Patents

Abstract

Probe has a housing, which in addition to the usual ultrasound vibrator, has at one digital camera (36), either fixed to the probe, or ideally mounted inside, directed so that it detects the surface (28) of the test piece. At periodic intervals electronic images of partial areas of the surface (28) are recorded. An image processing circuit with an image memory and a comparator determines the displacement of the probe relative to the object surface. Using a movement memory the displacement of the probe housing form a reference point at the beginning of measurement can be determined and the actual position of the probe with reference to this point determined.

Description

The invention relates to an ultrasonic probe, which in particular is suitable for testing by hand. It has a case that has an Ultra sonic transducer and that a contact surface for contact with the surface of a body to be tested.

Such ultrasonic probes are from the extensive state of the art known. In the ultrasound test, one would like to have an find the corresponding location on the body to be tested as precisely as possible know. So one would like to assign a location to an ultrasound finding can. So you endeavor to get one in the weld inspection to be able to pinpoint the found fault precisely. You would also like to the determination of the remaining wall thickness of a pipe or container exactly know the location on the container or pipe where a given Ultra was found. This means that in addition to the ultrasonic sig nal also the respective position of the ultrasonic probe on the surface of the body to be tested must be known.

According to the state of the art, there are systems that determine the position of the Ultra determine sound test head, e.g. B. as the relative position of the probe in two or three axes to one location at the start of measurement. Currently a dissolution  0.1 mm for longitudinal movements and 0.1 ° for rotary movements. Together with the relative position data and the respective Ultra The absolute location of a fault location can be determined precisely by sound the. Repair work or systematic monitoring of defects jobs can be carried out economically and in a targeted manner.

The methods currently used to determine the position data at ma Ultrasonic testing have several major disadvantages. So are for the position detection of additional electronic components, e.g. B. Airborne sound sensors and / or mechanical guides necessary, the ergonomic Have disadvantages. The mechanical parts can wear out, the air Sound sensors are relatively large, but in particular they have to be installed and closed adjust. The cost of the known methods and the front used for it directions are high.

Proceeding from this, the invention has set itself the task of one To create an ultrasonic probe that depends on the position coordinates from a location that is available at the start of the measurement on the body to be tested provides and issues. The disadvantages of the previously known systems are said to be be avoided.

This task is solved by an ultrasonic test head, especially for manual testing

• - With a housing that receives an ultrasonic transducer and that a contact area for contact with a surface of a test body,
• - With at least one digital camera that is assigned to the housing, the is aligned so that it captures the surface of the body and the in An electronic image of sections of the waiters is given at intervals area of the body supplies,  
• - With a circuit for image processing, the image memory for min at least has an electronic image captured by the digital camera, which has a comparator that differentiates two from the digital camera electronic images of overlapping Compare parts of the surface of the body and from it the ver displacement of the housing relative to the surface is determined and output and
• - With a movement memory, which is the displacement of the housing from a location at the time of the start of the measurement and the contains the current position of the housing with respect to this location.

This ultrasound probe is initially a classic rule ultrasonic test head, the usual features of such a test head. Reference is made, for example, to the DE book J. Kraut krämer & K. Krautkrämer "Material testing with ultrasound", 6th edition, Springer-Verlag. The ultrasonic test head can therefore be conventional like a usual ultrasonic test head can be used. For example, as a SE Test head executed.

In addition, the ultrasonic test head according to the invention also has means that serve the respective position on the surface of the body to be tested pers to indicate in relation to a place that at the time of the measurement start Template.

For this purpose, at least one digital camera is firmly connected to the housing. The digital camera is preferably arranged in the housing. It is so out that it detects the surface of the body to be tested. In doing so they provide an image of this surface as close as possible to the surface at which a Central beam of the active shell element passes through the surface.

With the help of this digital camera, an electronic image is created at intervals  (Frame) captured by the section of the surface that is under the Lens of the digital camera is located, that is, in the object plane. It is a relatively small section of the total surface of the body to be tested. The section can, for example, the dimensions of a few mm, for example 2 × 2 to 4 × 4 mm. Preferably the digital camera creates an image at predetermined fixed time intervals of the respective section of the surface.

In the circuit for image processing downstream of the digital camera is stored in an image memory at least one image that the digital has recorded the camera. This picture is taken with a picture captured later the digital camera compared in the comparator. The comparator postpones that the two electronic pictures against each other until the pictures come together that fit, i.e. matching image areas are in cover. This means that the time interval at which the two compare electronic pictures have been taken, must not be larger than the time within which the housing is shifted a distance that is larger than the image diagonal of the captured electronic image des. If the latter is the case, there are no matching partial areas more in the electronic images to be compared and no comparison can therefore take place.

From the necessary shift of the two individual images in the comparison can be compared to each other until coverage is achieved the actual displacement on the surface of the body under test calculate. Essentially, the imaging scale of the optics is involved. Accordingly, a position signal can be output that the different Exercise the test head between the time when the first electronic cal picture was taken and the time at which the second elect ronic image was recorded indicating. From the sum of the individual Displacement information is based on the location at the time of  Measurement starts the current position of the probe on the surface of the body to be tested.

An optical system forms the basis for position detection. The Digital cameras are preferably equipped with CCD sensors. The Ge The field of the digital camera is preferably assigned a lamp net to illuminate the portion of the surface to be detected. Now the probe moves, the position information in the moving are included, the current position is determined.

The electronic and optical means for positioning are used today, they can be very small and inexpensive hold. This means that the complete image evaluation can be carried out in one housing usual ultrasonic probe. By means of the Ultra sound test head according to the invention can in particular the evaluation of spatially small defects parallel to the surface of the body to be tested respectively. When testing weld seams, e.g. B. for pipes, Pipelines or in the tank and boiler construction the locations of the respective locations a finding can be given.

Here, the use of SE probes allows a simplified application determination of location coordinates. The send and receive The transducer of the ultrasonic probe is separated by a damping web housed in a housing. By at least one digital camera the position of two axes can be set especially for these test heads determine the most technical type. So you can, for example, the rest of the wall cheap Determine thickness on curved pipes.

The path information is added up in the movement memory. because tests can be carried out economically with improved ergonomics carry out. An examiner who guides the probe has optimal conditions  in carrying out his exam. There is no mechanical ver wear parts, the test reliability is in relation to the test without additional che information of the location coordinates increased significantly. Opposite mechani Position detection systems cost up to 60% saves. Comprehensive documentation of the exam is possible.

In a particularly preferred development, two digital cameras are provided seen that are spaced from each other on the housing, which each has its own circuit for image processing and with an evaluation stage for rotations at which the outputs of the two Circuits for image processing. From the different In Formations about the position of the housing from these two circuits for image processing, the housing is rotated relative to one earlier rotation status determined and output. A rotary memory contains the rotation information based on a rotation state at the time of Measuring starts.

When using two digital cameras, you can use Transformations functions very simply also the position of the angle of rotation of the test head determine your own axis. In principle, you could also use these a single digital camera, but then you would have to use the image ver perform in the comparator so that the electronic images do not only shifted in two directions against each other in pixel jumps until a sub-area shows agreement, rather would also have to Rotations of the two compared electronic images to each other be performed. This saves the effort and time of electronic Evaluation significantly increased in the comparator. To that extent, the installation of a second digital camera a simple and inexpensive solution.

In the version with two digital cameras, a rotary memory is provided, which determines the determined rotation information based on the state at the start of measurement  stores. In this way the respective total rotation is compared to that State known at start of measurement.

In a preferred development, a signal memory is provided, which in fixed assignment to the movement memory each at one position lying ultrasound information compiled with the position information tion stores. This makes it easy to access the Ultra sound test result possible. There can be an evaluation in different Shape. It is particularly preferred, whenever, whenever a critical ultrasound finding is obtained, for example a preset Threshold in the signal is exceeded, a display on a display device he follows. In this way, imperfections and other imperfections in the testing body optically z. B. displayed on a monitor. So that's one simple further processing of the information received is possible.

A start switch has proven to be very advantageous. It is preferred arranged on the housing of the ultrasonic test head. Him can at the same time and assign different functions independently. The movement memory is reset when the start switch is pressed and starts the summation of the movement information provided below mations new. Furthermore, the optical and electronic unit for position detection can be started. Thereby can be in an energy-saving shutdown function beforehand. This includes that the lighting means can be switched off.

It is possible, but not necessary, between the ultrasonic probe and Surface of the body to be tested, a coupling agent, for example Water to be provided. It has been shown that the function of the optical evidence of the position is not affected.

Further advantages and features of the invention result from the others  Claims and the following description of non-limiting to understand exemplary embodiments that with reference to the Drawing will be explained in more detail. In this show:

Fig. 1 is an ultrasonic probe which is formed as a TR probe is a schematic representation in side view,

FIG. 2 shows an ultrasound probe similar to FIG. 1, but now with two digital cameras,

Fig. 3 is a block diagram of an ultrasonic probe similar to Fig. 1,

Fig. 4 is a block diagram for an ultrasonic probe similar to Fig. 2 and

Fig. 5 is an illustration of a monitor showing a body to be tested, which has a defect.

The ultrasonic test heads are designed for non-destructive material testing. The test is carried out using the pulse-echo method. The Ultra schallprüfkopf according to Fig. 1 and 3 has a housing 20 for the reception of ultrasonic vibrators. A transmission oscillator 22 and an reception oscillator 23 are shown . The transmitting vibrator 22 is placed on a lead body 24 , the receiving vibrator 23 is placed on a lead body 25 . Both lead bodies 24 , 25 are located on a protective body 26 , which forms a lead and protective layer. This protective body 26 is in contact with a surface 28 of a body 30 to be tested. The protective body 26 consists of a transparent, preferably crystal-clear material, for example acrylic. A lower, freely accessible surface of the protective body 26 forms the contact surface for the contact of the housing 20 with the surface 28 of the body 30 to be tested.

As often found in SE probes, there is a damping web 32 , which forms a spacer, between the sensor deschwinger 22 and its lead body 24 on one side and the receiving transducer 23 and its lead body 25 on the other side. This has a hole through which a light guide 34 is passed. Instead of an optical fiber, an optical fiber bundle can also be used. The light guide 34 ends within the protective body 26 and in the vicinity of the surface 28 to which it is directed (see dashed lines). It transmits the image of a small portion of the surface 28 to a digital camera 36 , which is located within the housing 20 . It is also called CAM. An optical reflective sensor HDNS-2000 from HP is used as a digital camera. It is associated with a lens 38 , which is supplied by the same company under HDNS-2100. But other digital cameras can also be used.

The digital camera 36 has a light-sensitive arrangement, which is designed in particular as a CCD and has a flat arrangement (matrix) of pixels. In this arrangement, the lens 38 images the section of the surface 28 under consideration.

The digital camera 36 captures electronic images, which are also referred to below as frames, of the portion of the surface 28 under consideration at periodic time intervals. A frame is typically captured every 8 ms.

The digital camera 36 is a circuit for image processing 40 nachge. It has an image memory 42 , which is also referred to as FMEM, for at least one frame captured by the digital camera 36 . In particular, it is the penultimate frame captured by the camera, which is stored in the image memory 42 . It is compared with the current frame in a comparator 44 , which is also referred to as COMP.

The two frames are shifted pixel by pixel parallel to the rows and lines of the pixels until matching image areas of the frame are found. This presupposes that the frames contain overlapping portions of the surface of the body 30 to be tested. The displacement of the two frames in the image plane of the digital camera 36 can then be used to calculate the displacement in the object plane, that is to say on the surface 28 of the body 30 to be tested. Essentially, the imaging ratio of the digital camera 36 including its lens 38 must be taken into account.

As a result, the circuit 40 for image processing transfers information to a movement memory, which is also referred to as MMEM, about the displacement of the housing 20 between the times at which the two compared frames were acquired. The movement memory 46 continuously stores the displacements transferred to it. The displacements are transferred in a right-angled coordinate system as x values and y values. The current position of the housing 20 is therefore always contained in the movement memory 46 .

The totalization of the movements in the movement memory 46 takes place starting from a location 48 which the housing has at the time of a measurement start. The start of measurement is entered by a start switch 50 . If the start switch 50 is actuated, the movement memory 46 is first reset or brought into a zero state. It then stores all the movement information transferred to it, that is to say the increments in two directions. The information of the movement memory 46 can be displayed on a monitor 52 , which will be discussed later.

As shown in FIG. 1, the section of surface 28 under consideration is illuminated by an illuminant 52 , which is embodied here as an LED. The illumination is preferably grazed to the surface 28 so that the digital camera 36 can capture as many contours as possible. It is advantageous to switch on the illuminant 52 only when the start switch 50 has been actuated. The circuit 40 switches into a power-saving mode when a number of successively arriving frames completely match and thus no movement of the housing 20 can be determined.

As Fig. 1 shows, the light source 52 is disposed in the housing 20 so that the transparent protective body is irradiated 26th It can also be accommodated in the protective body 26 . If a coupling agent is to be used between the protective body 26 and the surface 28 , a completely transparent agent, for example water, is preferably used.

In contrast to the design of the test head according to FIGS. 1 and 3, the test head according to FIGS. 2 and 4 has two digital cameras 36 and 37 , see also CAM and CAM 2 . They are housed at a distance from each other in the housing 20 , specifically they are positioned on both sides of an oscillator 23 . A damping body 54 is assigned to this oscillator 23 , which can also be a transmission oscillator. In the direction of sound propagation there is a lead body 25 , which in turn is in contact with a protective body 26 .

The arrangement of two digital cameras 36 , 37 and two illuminants 52 is essentially a doubling of the arrangement according to FIG. 1. In contrast to the embodiment according to FIG. 1, however, optical fiber optics are now not used to image a portion of the surface 28 to the digital camera 36 to transmit, rather the respective lenses 38 of the digital cameras 36 , 37 are accommodated in the protective body 26 . They can also be applied to or near its top surface.

The additional function obtained by the second digital camera 37 , also called CAM 2 , is explained below with reference to FIG. 4. This figure shows the two digital cameras 36 , 37 , each of which is followed by a circuit 40 for image processing. The surface 28 of the body 30 is shown. A section of this surface is recorded because the sections are spaced from each other. At the output of the respective circuit 40 for image processing, the information is available on the position increments of each individual digital camera 36 , 37 . This information is now processed as follows: For the determination of the position, only the lower digital camera 36 in FIG. 4 is used, in so far no change can be determined according to FIG. 2. The upper digital camera 37 is used only insofar as it provides information about the rotation of the housing 20 in connection with the lower digital camera 36 . For this purpose, the shift information of both circuits 40 for image processing is sent to an evaluation stage 56 , also called RED. In this, the individual increments are compared and the respective rotation of the housing 20 , which can be determined between the frames under consideration, is determined. A rotary memory 58 , also called ROTM, is connected downstream of this evaluation stage 56 . The rotational state of the housing 20 is stored in this, starting from the state at the location 58 at the time of the start of the measurement.

As already stated, frames are captured by the digital cameras 36 , 37 every 8 ms. The image is then evaluated. Very little time is required for this, the time for image evaluation is less than 1 ms. A short image evaluation is achieved in that the frames to be compared in the comparator stage 44 only have to be shifted pixel by pixel in the row and row direction of the pixels. The frames are not rotated against each other. Basically, however, a rotation of the individual frames against one another is also possible in the comparator 44 . Then a second digital camera 37 is not required.

In FIGS. 3 and 4 is also in each case a marked still an ultrasound assembly. Shown is a vibrator 23 , which is shown here without any additional body. It is connected on the one hand to a transmitter 60 , also called TRANSM here, and on the other hand to a receiver 62 , also called REC here. A memory 64 , which is also referred to as SMEM, is connected downstream of the receiver 62 . This memory 64 is also connected to the movement memory 46 . The ultrasound is found in the memory 64 , as it is obtained from the receiver 62 after evaluation, and the respective position at which this ultrasound finding was obtained is stored abge. The respective position relates to location 48 .

In an advantageous development, a device for determining the position, for example a circuit for global positioning according to the GPS method, is assigned to the ultrasonic test head. In this way, the location 48 that is present at the start of the measurement is determined absolutely. This absolute determination is recorded in the movement memory 46 or in the memory 64 .

FIG. 5 shows the representation of an ultrasound measurement process with the ultrasound test head according to the invention on a monitor 66 . An ultrasonic testing device of the applicant of the type USD 15 with a vibrating arrangement with a leading body etc. of the type CLF 4 was used , which was additionally equipped with the device according to the invention for determining the position, that is to say is constructed in accordance with FIG. 1.

A steel plate with a rectangular cut was used as the workpiece to be checked, ie as body 30 . A hole of 3 mm in diameter and 2.5 mm in depth was made in this. The aperture of the USD 15 device was set as follows: start 2 mm, width 1 mm. The hole had to deliver an error signal.

The test head was first positioned at a corner of the body 30 .

Then the start switch 50 was pressed and moved to an adjacent corner. This was repeated until the circumference of the body 30 was worn. As a result, the contour 68 shown in dashed lines, which is visible on the monitor 66 , could be obtained.

The lower left corner point of the body 30 was selected as the location 48 for the start of the measurements. The start switch 50 was actuated there. The beginning of the check is shown schematically using a path 70 . The complete test path with which the test head was guided over the surface 28 of the body 30 is not shown. It is possible to display the test route. However, this would impair the legibility of the drawing in the specific case. In FIG. 5, write information has only ever been given to the monitor 66 or the upstream computer if the device USD 15 has delivered an error signal. As a result, there were short black lines when the bore was passed over, which overall represent an image 72 of the error. You can see an approximately circular, black spot. In this way, an exact localization of the error is achieved.

Claims (7)

1. Ultrasonic test head, especially for testing by hand

• with a housing ( 20 ) which receives an ultrasonic oscillator and which has a contact surface for contact with a surface ( 28 ) of a body ( 30 ) to be tested,
• - With at least one digital camera ( 36 ), the housing ( 20 ) is zugeord net, which is preferably housed in the housing ( 20 ), which is oriented so that it detects the surface ( 28 ) of the body ( 30 ) and the provides an electronic image of portions of the surface ( 28 ) of the body ( 30 ) at intervals,
• - With a circuit for image processing ( 40 ) having an image memory ( 42 ) for at least one of the digital camera ( 36 ) captured electronic image, which has a comparator ( 44 ), two of the digital camera ( 36 ) at different times captured electronic images of overlapping portions of the surface ( 28 ) of the body to be tested ( 30 ) and compares and determines the displacement of the housing ( 20 ) against the surface ( 28 ) and outputs and
• - With a movement memory ( 46 ) which stores the displacement of the housing ( 20 ) starting from a location ( 48 ) at the time of the measurement start and contains the current position of the housing ( 20 ) with respect to this location ( 48 ).

2. Ultrasonic test head according to claim 1, characterized in that two digital cameras ( 36 , 37 ) are provided, which are arranged at a distance from one another on the housing ( 20 ), each of which has its own circuit for image processing ( 40 ) downstream and with an evaluation stage ( 56 ) for rotations at which the outputs of the two circuits for image processing ( 40 ) are present and which, from the different information about the position of the housing ( 20 ) from these two circuits for image processing, cause the housing ( 20 ) to rotate relative to an earlier rotation state determined and outputted and with a rotary memory ( 58 ) which contains the rotary information based on a rotary state at the time of the measurement start. 3. Ultrasonic test head according to claim 1, characterized in that the housing ( 20 ) is assigned a lamp ( 52 ), in particular a lamp ( 52 ) is arranged in the housing ( 20 ), which is oriented such that the digital camera ( 36 ) detected area of the surface ( 28 ) of the body ( 30 ) is illuminated. 4. Ultrasonic test head according to claim 3, characterized in that the illuminant ( 52 ) shines onto the surface ( 28 ) of the body ( 30 ) at the lowest possible angle. 5. Ultrasonic test head according to claim 1, characterized in that a start switch ( 50 ) is provided, which is preferably arranged on the housing ( 20 ), and that with this start switch ( 50 ) the movement memory ( 46 ) the location ( 48 ) at the time of actuation of the start switch ( 50 ), stores as a new starting point for further movements. 6. Ultrasonic test head according to claim 1, characterized in that it has a protective body 26 which forms a freely accessible limiting surface of the housing ( 20 ) which represents the contact surface, and that this protective body ( 26 ) is transparent, as crystal-clear as possible, in particular is made of acrylic. 7. Ultrasonic test head according to claim 6, characterized in that the digital camera ( 36 , 37 ) on the inside of the protective body ( 26 ) is angeord net.